Escape Key Project - A - Air Grille

Hidden in Plain Sight: Building a Secret Message Air Vent for Escape Key

This week on the Escape Key project, I built something that’s been rattling around in my head for a while: a disguised air vent that hides a secret message.

At first glance, it’s just an ordinary office-style ventilation grille—like the kind you might find in any building. You can slide it open or closed to control airflow. But here’s the twist: when you slide it open, light shines through holes that spell out a message. Hidden in plain sight. Classic escape room fodder.

Originally, I thought the holes could simply form letters. But then I took it further—what if a light flickered behind the grille to attract attention? Something subtle enough to be ignored, but curious enough to draw the eye. In future versions, I’d love to add a diffuser for smoother lighting, and a switch so the lights only activate at the right moment. More on that later.

The Design Process: Shapr3D vs. Tinkercad

I began by sketching out the concept and turned to Shapr3D, a powerful CAD tool. It’s incredibly capable but comes with a steep learning curve. While there are plenty of tutorials, many focus on complex, high-end examples—great for pros, less so for beginners like me who just want to align two rectangles.

Eventually, I gave up trying to force Shapr3D to cooperate and pivoted to Tinkercad. It’s often dismissed as a kids’ tool, but for what I needed—rectangles, hollows, unions—it was ideal. You can make hollow shapes, align them easily, and create precise cutouts quickly. In fact, despite all its bells and whistles, Shapr3D never gave me the simple shape-alignment workflow that Tinkercad nailed in seconds.

Prototyping and Printing

It took me seven design iterations: three for the message layer and four for the slotted front grille. A few of those were just down to careless measurement errors—expanding a boundary instead of contracting it, that sort of thing. Lessons learned: double-check before you print!

Each piece took about an hour to print and cost just over £2 in PLA filament. I used a Bambu X1 Carbon printer—fast, quiet, and reliable enough to “set and forget.” The slicer software even calculates the cost based on how much filament is used. Handy.

To make the piece practical, I designed it to fit a standard UK double socket junction box. These are cheap (£1.19 from my local shop) and easy to mount, making installation straightforward for anyone wanting to build this into a wall or prop.

Wiring It Up

Using an Arduino Uno and a breadboard, I wired up seven red LEDs with resistors and a simple script (happy to share the code). While the effect worked, I noticed something my 13-year-old son wisely pointed out: the white plastic grille wasn’t thick enough to block the LED light fully. The result? Letters were hard to read in low light, as the LEDs bled through the plastic.

His advice was spot-on. I ended up using electrical insulating tape to mask the unwanted light areas. It worked brilliantly—now the letters pop clearly against a darkened backdrop.

Improvements for Next Time

If I were to do this again (and I probably will), here’s what I’d change:

1. Double-check measurements and alignment to avoid wasted prints.

2. Add a diffuser—a lightly scratched or frosted plastic sheet—to soften the LED glow and avoid the visible “dot” effect.

3. Include a trigger mechanism, such as a foil switch that’s activated when the grille slides. That way, the message only appears when the user interacts with the vent—more mystery, more magic.

To watch the YouTube video of this build for an Escape room Air Grille, click here.

This has probably been the most complex build I’ve tackled so far, but I’m thrilled with how it turned out. If you’ve got ideas for improvements or alternative uses, I’d love to hear them. What would you hide behind an air vent?